Set screw with strain gauges

ABSTRACT

Embodiments pertaining to a medical construct are disclosed. The medical construct may include a set screw extending along a longitudinal axis between a proximal portion and a distal portion, for example. In various embodiments, the set screw may have an outside thread form and an interior socket, for example. In various embodiments, the socket may extend parallel to the longitudinal axis and have a circular lower surface, for example. In various embodiments, a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, and a fifth strain gauge may be provided. In at least some embodiments, each of the first, second, third, and fourth strain gauges may be symmetrically disposed with respect to the lower surface, for example. Additionally, in at least some embodiments, the fifth strain gauge is disposed within a center portion of the lower surface, for example.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part application of U.S. patent application Ser. No. 17/151,475, filed Jan. 18, 2021 which is a continuation application of U.S. patent application Ser. No. 16/405,576, filed May 7, 2019 (now U.S. Pat. No. 10,893,915). This application is also a continuation in part application of U.S. patent application Ser. No. 16/395,216, filed Apr. 25, 2019 which is a continuation in part application of U.S. patent application Ser. No. 16/039,592, filed Jul. 19, 2018. The entire disclosure of each is incorporated herein by reference in entirety.

TECHNICAL FIELD

The present disclosure generally relates to medical devices for the treatment of musculoskeletal disorders, and more particularly to a surgical system and a method for treating a spine.

BACKGROUND

Spinal pathologies and disorders such as scoliosis, kypho-sis and other curvature abnormalities, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, tumor and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including deformity, pain, nerve damage, and partial or complete loss of mobility.

Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatment of these spinal disorders includes correction, fusion, fixation, discectomy, laminectomy and implantable prosthetics. As part of these surgical treatments, spinal constructs such as vertebral rods are often used to provide stability to a treated region. Rods redirect stresses away from a damaged or defective region while healing takes place to restore proper alignment and generally support vertebral members. During surgical treatment, one or more rods and bone fasteners can be delivered to a surgical site. The rods may be attached via the fasteners to the exterior of two or more vertebral members. Setscrews can be used to secure the rods with the fasteners. However, the connection force and continued integrity of the connection between the rods and the fasteners can be challenging to monitor during and after implantation. In addition, it is difficult to monitor that a proper or acceptable force is maintained between the setscrews and the rods. This disclosure describes an improvement over these prior technologies.

SUMMARY

In one embodiment, a spinal construct is provided. The spinal construct includes a first member. The first member comprises a first thread form and an implant cavity configured for disposal of a spinal implant. A second member is engageable with the spinal implant. The second member comprises a second thread form configured for engagement with the first thread form. A gauge is coupled to the second member. The gauge is configured to measure a force between the second member and the spinal implant when the second member is engaged with the first member. The second thread form is timed and/or clocked with the first thread form to position the gauge in a selected orientation relative to the spinal implant.

In one embodiment, a surgical method is provided that includes: coupling a first member to tissue; positioning a spinal implant in an implant cavity of the first member; and engaging a first thread form of the first member with a second thread form of a second member such that the second member applies a force to the spinal implant, wherein the second member comprises a gauge, and wherein the second thread form is timed and/or clocked with the first thread form to position the gauge in a selected orientation relative to the spinal implant.

In one embodiment, a spinal construct is provided. The spinal construct includes a bone screw. The bone screw comprises a pair of arms. The arms define a U-shaped implant cavity configured for disposal of a spinal rod. Inner surfaces of the arms define a first thread form. A setscrew is engageable with the spinal rod. The setscrew comprises an inner surface and an outer surface. The inner surface of the setscrew defines a socket. The outer surface defines a second thread form configured for engagement with the first thread form. A gauge is positioned within the socket. The gauge is configured to measure a force between the setscrew and the spinal rod when the setscrew is engaged with the bone screw. The second thread form is timed and/or clocked with the first thread form to position the gauge in a selected orientation relative to the spinal rod.

In another embodiment, a medical construct is provided. The medical construct may include a set screw extending along a longitudinal axis between a proximal portion and a distal portion, for example. In various embodiments, the set screw may include an outside thread form and a socket disposed within an interior of the set screw relative to the outside thread form, for example. In various embodiments, the socket may extend parallel to the longitudinal axis and have a lower surface, for example. In various embodiments, a plurality of strain gauges may be disposed on the lower surface, and the plurality of gauges may be configured to measure a force applied to the set screw, for example. In various embodiments, each of the plurality of strain gauges may be symmetrically disposed with respect to the lower surface, for example.

In another embodiment, a medical construct is provided. The medical construct may include a set screw extending along a longitudinal axis between a proximal portion and a distal portion, for example. In various embodiments, the set screw may have an outside thread form and an interior socket, for example. In various embodiments, the socket may extend parallel to the longitudinal axis and have a circular lower surface, for example. In various embodiments, a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, and a fifth strain gauge may be provided. In at least some embodiments, each of the first, second, third, and fourth strain gauges may be symmetrically disposed with respect to the lower surface, for example. Additionally, in at least some embodiments, the fifth strain gauge is disposed within a center portion of the lower surface, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more readily apparent from the specific description accompanied by the following drawings, in which:

FIG. 1 is a side view of components of one embodiment of a surgical system, in accordance with the principles of the present disclosure;

FIG. 2 is a top view of components of the system shown in FIG. 1;

FIG. 3 is a perspective view of one embodiment of a first component of the system shown in FIG. 1, in accordance with the principles of the present disclosure;

FIG. 4 is a side view of one embodiment of a second component of the system shown in FIG. 1, in accordance with the principles of the present disclosure;

FIG. 5 is a side, cross-sectional view of the component shown in FIG. 4 taken along lines A-A in FIG. 4;

FIG. 6 is a top view of the second component shown in FIG. 4 and one embodiment of a third component of the system shown in FIG. 1, in accordance with the principles of the present disclosure;

FIG. 7 is a top view of the second component shown in FIG. 4 and one embodiment of the third component of the system shown in FIG. 1, in accordance with the principles of the present disclosure;

FIG. 8 is a top view of the second component shown in FIG. 4 and one embodiment of the third component of the system shown in FIG. 1, in accordance with the principles of the present disclosure;

FIG. 9 is a perspective view of one embodiment of the third component of the system shown in FIG. 1, one embodiment of a fourth component of the system shown in FIG. 1, one embodiment of a fifth component of the system shown in FIG. 1, one embodiment of a sixth component of the system shown in FIG. 1, and one embodiment of a seventh component of the system shown in FIG. 1, in accordance with the principles of the present disclosure;

FIG. 10 is a side view of the second component shown in FIG. 4, the third component shown in FIG. 9, the fourth component shown in FIG. 9, the fifth component shown in FIG. 9, the sixth component shown in FIG. 9, and the seventh component shown in FIG. 9;

FIG. 11 is a side view of the second component shown in FIG. 4, the third component shown in FIG. 9, one embodiment of the fourth component shown in FIG. 9 in accordance with the principles of the present disclosure, the fifth component shown in FIG. 9, the sixth component shown in FIG. 9, and the seventh component shown in FIG. 9;

FIG. 12 is a top view of the second component shown in FIG. 4, the third component shown in FIG. 9, the fourth component shown in FIG. 9, the fifth component shown in FIG. 9, the sixth component shown in FIG. 9, and the seventh component shown in FIG. 9; and

FIG. 13 is a top down view of an alternate embodiment showing a plurality of strain gauges.

DETAILED DESCRIPTION

The exemplary embodiments of the surgical system and related methods of use disclosed are discussed in terms of medical devices for the treatment of musculoskeletal disorders and more particularly, in terms of a surgical system and a method for treating a spine. In some embodiments, the systems and methods of the present disclosure comprise medical devices including surgical instruments and implants that are employed with a surgical treatment, as described herein, for example, with a cervical, thoracic, lumbar and/or sacral region of a spine.

In some embodiments, the present surgical system comprises the ability to collect data from a fixation implant to allow surgeons to monitor the implant status and/or fusion state. In some embodiments, gauge s, such as, for example, strain gauges, are placed on the implants to collect and transmit data intra-operatively and post-operatively. The gauge s can detect loading conditions of the implanted construct. The orientation of the gauge is controlled to avoid variable loading detection.

In some embodiments, the implant construct contains a pedicle screw, rod, and setscrew. The setscrew contains gauge s, such as, for example, strain gauges, which detect loading. The thread on the setscrew and pedicle screw are timed and/or clocked to allow consistent orientation once the setscrew is locked. Gauges are mounted in a controlled orientation with respect to the start of the setscrew thread. This allows orientation of the gauge s to be controlled with respect to the rod. It is envisioned that the number and configuration of gauge s may vary, as discussed herein.

In some embodiments, the present surgical system allows loading data to be captured from an implant. The control of the orientation ensures reproducibility in the measurements. In some embodiments, gauge orientation is controlled with respect to the thread start of the setscrew. In some embodiments, the thread start of the setscrew defines a controlled dimension of the setscrew. In some embodiments, the setscrew includes an inner surface that defines a socket, the gauge being applied to the inner surface. In some embodiments, the gauge orientation is controlled such that the gauge orientation is inline with an orientation of a rod. In some embodiments, the gauge orientation is controlled such that the gauge orientation is transverse to the orientation of a rod. In some embodiments, the gauge orientation is controlled such that the gauge orientation is non-parallel (e.g., at an acute angle) relative the orientation of a rod. In some embodiments, the system includes a tulip head having threads that are timed and/or clocked to a rod slot of the tulip.

In some embodiments, the surgical system of the present disclosure may be employed to treat spinal disorders such as, for example, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor and fractures. In some embodiments, the surgical system of the present disclosure may be employed with other osteal and bone related applications, including those associated with diagnostics and therapeutics. In some embodiments, the disclosed surgical system may be alternatively employed in a surgical treatment with a patient in a prone or supine position, and/or employ various surgical approaches to the spine, including anterior, posterior, posterior mid-line, direct lateral, postero-lateral, and/or antero-lateral approaches, and in other body regions. The surgical system of the present disclosure may also be alternatively employed with procedures for treating the lumbar, cervical, thoracic, sacral and pelvic regions of a spinal column. The surgical system of the present disclosure may also be used on animals, bone models and other non-living substrates, such as, for example, in training, testing and demonstration.

The surgical system of the present disclosure may be understood more readily by reference to the following detailed description of the embodiments taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this application is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting. In some embodiments, as used in the specification and including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It is also understood that all spatial references, such as, for example, horizontal, vertical, top, upper, lower, bottom, left and right, are for illustrative purposes only and can be varied within the scope of the disclosure. For example, the references “upper” and “lower” are relative and used only in the context to the other, and are not necessarily “superior” and “inferior”.

As used in the specification and including the appended claims, “treating” or “treatment” of a disease or condition refers to performing a procedure that may include administering one or more drugs to a patient (human, normal or otherwise or other mammal), employing implantable devices, and/or employing instruments that treat the disease, such as, for example, microdiscectomy instruments used to remove portions bulging or herniated discs and/or bone spurs, in an effort to alleviate signs or symptoms of the disease or condition. Alleviation can occur prior to signs or symptoms of the disease or condition appearing, as well as after their appearance. Thus, treating or treatment includes preventing or prevention of disease or undesirable condition (e.g., preventing the disease from occurring in a patient, who may be predisposed to the disease but has not yet been diagnosed as having it). In addition, treating or treatment does not require complete alleviation of signs or symptoms, does not require a cure, and specifically includes procedures that have only a marginal effect on the patient. Treatment can include inhibiting the disease, e.g., arresting its development, or relieving the disease, e.g., causing regression of the disease. For example, treatment can include reducing acute or chronic inflammation; alleviating pain and mitigating and inducing re-growth of new ligament, bone and other tissues; as an adjunct in surgery; and/or any repair procedure. In some embodiments, as used in the specification and including the appended claims, the term “tissue” includes soft tissue, ligaments, tendons, cartilage and/or bone unless specifically referred to otherwise.

The following discussion includes a description of a surgical system including a surgical instrument, implants, related components and methods of employing the surgical system in accordance with the principles of the present disclosure. Alternate embodiments are also disclosed. Reference is made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. Turning to FIGS. 1-12, there are illustrated components of a surgical system, such as, for example, a surgical system 20.

The components of surgical system 20 can be fabricated from biologically acceptable materials suitable for medical applications, including metals, synthetic polymers, ceramics and bone material and/or their composites. For example, the components of surgical system 20, individually or collectively, can be fabricated from materials such as stainless steel alloys, aluminum, commercially pure titanium, titanium alloys, Grade 5 titanium, super-elastic titanium alloys, cobalt-chrome alloys, superelastic metallic alloys (e.g., Niti-nol, super elasto-plastic metals, such as GUM METAL®), ceramics and composites thereof such as calcium phosphate (e.g., SKELITE™), thermoplastics such as polyaryletherke-tone (PAEK) including polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and polyetherketone (PEK), carbon-PEEK composites, PEEK-BaSO4 polymeric rubbers, polyethylene terephthalate (PET), fabric, silicone, polyurethane, silicone-polyurethane copolymers, polymeric rubbers, polyolefin rubbers, hydrogels, semi-rigid and rigid materials, elastomers, rubbers, thermoplastic elastomers, thermoset elastomers, elastomeric composites, rigid polymers including polyphenylene, polyamide, polyimide, polyetherimide, polyethylene, epoxy, bone material including autograft, allograft, xenograft or transgenic cortical and/or corticocancellous bone, and tissue growth or differentiation factors, partially resorbable materials, such as, for example, composites of metals and calcium-based ceramics, composites of PEEK and calcium based ceramics, composites of PEEK with resorbable polymers, totally resorbable materials, such as, for example, calcium based ceramics such as calcium phosphate, tri-calcium phosphate (TCP), hydroxyapatite (HA)-TCP, calcium sulfate, or other resorb-able polymers such as polyaetide, polyglycolide, polytyro-sine carbonate, polycaroplaetohe and their combinations.

Various components of surgical system 20 may have material composites, including the above materials, to achieve various desired characteristics such as strength, rigidity, elasticity, compliance, biomechanical performance, durability and radiolucency or imaging preference. The components of surgical system 20, individually or collectively, may also be fabricated from a heterogeneous material such as a combination of two or more of the above-described materials. The components of surgical system 20 may be monolithically formed, integrally connected or include fastening elements and/or instruments, as described herein.

Surgical system 20 is employed, for example, with a fully open surgical procedure, a minimally invasive procedure including percutaneous techniques, and mini-open surgical techniques to deliver and introduce instrumentation and/or one or more spinal implants, such as, for example, one or more components of a bone fastener, at a surgical site of a patient, which includes, for example, a spine. In some embodiments, the spinal implant can include one or more components of one or more spinal constructs, such as, for example, interbody devices, interbody cages, bone fasteners, spinal rods, tethers, connectors, plates and/or bone graft, and can be employed with various surgical procedures including surgical treatment of a cervical, thoracic, lumbar and/or sacral region of a spine.

Surgical system 20 includes a first member, such as, for example, a bone screw 22 including a head, such as, for example, a tulip head 24 and a shaft 26 configured to be connected with head 36, as discussed herein. Head 24 includes a pair of spaced-apart arms 28, 30. Arm 28 includes an inner surface 32 and arm 30 includes an inner surface 34. Surfaces 32, 34 define a U-shaped passageway, such as, for example, an implant cavity 36. Cavity 36 is configured for disposal of a spinal implant, such as, for example, a spinal rod 38. In some embodiments, all or only a portion of cavity 36 may have alternate cross section configurations, such as, for example, oval, oblong, triangular, square, polygonal, irregular, uniform, non-uniform, offset, staggered, and/or tapered. In some embodiments, arms 28, 30 may be disposed at alternate orientations, relative to a longitudinal axis of screw 22, such as, for example, transverse, perpendicular and/or other angular orientations such as acute or obtuse, co-axial and/or may be offset or staggered. Arm 28 includes a thread 40 and arm 30 includes a thread 42 that faces thread 40. Threads 40, 42 define a first thread form 44 configured for engagement with a thread form of a second member, such as, for example, a setscrew 46 to fix rod 38 relative to head 24, as discussed herein. In some embodiments, setscrew 46 can be made, sold, or provided with independently from one or both of screw 22 and rod 38.

Shaft 26 has a cylindrical cross-sectional configuration and includes an outer surface having an external thread form 48. In some embodiments, thread form 48 may include a single thread or a plurality of discrete threads. In some embodiments, other engaging structures may be located on shaft 26, such as, for example, a nail configuration, barbs, expanding elements, raised elements and/or spikes to facilitate engagement of shaft 26 with tissue.

In some embodiments, all or only a portion of shaft 26 may have alternate cross section configurations, such as, for example, oval, oblong, triangular, square, polygonal, irregular, uniform, non-uniform, offset, staggered, undulating, arcuate, variable and/or tapered. In some embodiments, the outer surface of shaft 26 may include one or a plurality of openings. In some embodiments, all or only a portion of the outer surface of shaft 26 may have alternate surface configurations to enhance fixation with tissue, such as, for example, rough, arcuate, undulating, mesh, porous, semi-porous, dimpled and/or textured. In some embodiments, all or only a portion of shaft 26 may be disposed at alternate orientations, relative to its longitudinal axis, such as, for example, transverse, perpendicular and/or other angular orientations such as acute or obtuse, co-axial and/or may be offset or staggered. In some embodiments, all or only a portion of shaft 26 may be cannulated.

Setscrew 46 comprises an upper portion 50 and a lower portion 52. Portion 52 includes a second thread form 54 that extends outwardly from an outer circumferential surface of portion 52. Thread form 54 is configured to mate with thread form 44 to fix rod 38 relative to head 24, as discussed herein. Portion 50 has a length and width that is configured to facilitate manipulation of setscrew 46. A bottom tip 56 is formed on a bottom end 58 of setscrew 46 and is located centrally on bottom end 58 so as to extend outward along a central longitudinal axis X of rotation of setscrew 46. Setscrew 46 is configured to exert a compression or clamping force onto rod 38 through tip 56. In particular, tip 56 impinges on rod 38 and may, in some embodiments, form a dimple or depression in rod 38. In some embodiments, tip 56 is substantially dome shaped with a surface that is convex or rounded so that a small surface area is in contact with rod 38 providing a strong grip when pressed against rod 38. Alternatively, in some embodiments, tip 56 could be of various shaped points including flat, cone, cup, dog, or knurled. In some embodiments, portion 50 has a hexagonal external cross-section and round internal cross-section. In some embodiments, the internal cross-section of portion 50 and/or the external cross-section of portion 50 can be variously shaped, such as, for example, circular, oval, oblong, triangular, square, polygonal, irregular, uniform, non-uniform, offset, staggered, undulating, arcuate, variable and/or tapered.

In some embodiments, an inner surface 60 of setscrew 46 defines a hollow bore, such as, for example, a socket 62 in the body of setscrew 46. Socket 62 extends from an opening in portion 50 and, in various embodiments, into at least a section of portion 52. The section of socket 62 extending into portion 52 comprises a driving recess 64 for assisting in the removal by internal wrenching of portion 52 after portion 50 has been broken away at a frangible portion 66, as discussed herein. In some embodiments, recess 64 has a shape that can be a hexagon, hexalobular, clutch, fluted, frearson, slotted, star, Torx, reverse thread, Pozidriv, or Phillips.

Portion 66 is an area of reduced wall thickness and can have a cross-section in the form of a notch creating a weakened zone. Portion 50 can have at least one flat surface 68 for the application of torque to setscrew 46. In some embodiments, surface 68 is on the exterior of portion 50. Portion 66 connects portion 50 and portion 52. Portion 66 is easily or readily ruptured, separated or broken when a pre-selected torque or force is applied. When portion 50 is removed, portion 52 remains as shown in FIGS. 10 and 11. An exemplary description of a setscrew having such a frangible portion is disclosed in U.S. Pat. No. 6,179,841 and U.S. patent application Ser. No. 12/609,728, which are each incorporated herein by reference, in their entireties.

System 20 includes one or a plurality of gauges, such as, for example, strain gauges 70 that is/are coupled to setscrew 46 to measure a force between setscrew 46 and rod 38 when setscrew 46 is engaged with head 24, as discussed herein. That is, thread form 54 is configured to engage thread form 44 to translate setscrew 46 relative to head 24 until setscrew 46 directly engages rod 38 within cavity 36 to fix rod 38 relative to head 24. Gauges 70 may each include one or more gauge s or gauge nodes that measure strain, force, resistance, load and or the like. References in the present specification to a gauge or sensor thereby disclose embodiments in which multiple gauges or sensors, respectively are used, and when multiple gauges/sensors are referenced in the present specification, various embodiments also include a single gauge or sensor. Gauges 70 measure the amount of force setscrew 46 exerts on rod 38, which are indicative of loading conditions of rod 38. For example, setscrew 46 may exert a first amount of force on rod 38 when system 20 is initially implanted within a patient. However, the amount of force setscrew 46 exerts on rod 38 may decrease over time for a variety of reasons. Such a decrease in the amount of force setscrew 46 exerts on rod 38 may indicate increased fusion of adjacent vertebrae, for example. Indeed, because the load on rod 38 is gradually transferred to bone as bone graft (e.g., autograft) heals, the load on the rod decreases over time.

As discussed herein, strain data from gauges 70 can provide an in vivo assessment of the bony incorporation of an autograft, for example, and thus the fusion of the autograft and vertebrae. For example, an expected pattern of strain detected by gauges 70 will initially involve large axial forces that will decrease over time as components of system 20, such as, for example, rod 38, share more of the load with the vertebrae that are being fused by the autograft. If the data from gauges 70 follows or deviates from the expected patterns, conclusions can be drawn about progress of the fusion between the autograft and the vertebrae. System 20 thus provides the ability to continuously, or on-demand, monitor fusion progress and biomechanical performance during the post-operative period by assessing strain data from gauges 70. Indeed, strain readings from gauges 70 may be used to develop an accurate, early assessment of the fracture healing rate and the potential for not uniting. An early diagnosis of delayed union is advantageous because it allows the surgeon to take remedial steps as soon as a possible non-union is suspected, thus prompting intervention. Because of this ability to continuously or on-demand monitor fusion progress and biomechanical performance, it may be possible to appropriately time, or even avoid, additional surgery. Further, information gathered from such in vivo assessments can lead to improvements in surgical techniques and spinal implant design.

Gauges 70 may be selectively positioned on setscrew 46 to measure a force between setscrew 46 and rod 38 when setscrew 46 is engaged with head 24. In some embodiments, gauges 70 are positioned in socket 62. In some embodiments, gauges 70 are positioned in recess 64. In some embodiments, gauges 70 directly engage a surface 72 of setscrew 46 that defines a groove 74 that is distal to recess 64, as shown in FIG. 5. Positioning gauges 70 in groove 74 prevents a bit of a driving tool from directly engaging gauges 70 when the bit is positioned in recess 64 so as not to deform or otherwise compromise gauges 70.

In some embodiments, gauges 70 are aligned linearly on setscrew 46. For example, in one embodiment, shown in FIG. 6, setscrew 46 includes a first gauge 70 a, a second gauge 70 b, a third gauge 70 c and a fourth gauge 70 d that are aligned along a transverse axis Xl. It is envisioned that gauges 70 may also be positioned radially about setscrew 46. For example, in one embodiment, shown in FIG. 7, setscrew 46 includes a first gauge 70 a, a second gauge 70 b, a third gauge 70 c and a fourth gauge 70 d, wherein gauges 70 a, 70 b, 70 c, 70 d form a radial pattern, with gauges 70 a, 70 b, 70 c, 70 d each positioned 90 degrees from an adjacent one of gauges 70 a, 70 b, 70 c, 70 d. In one embodiment, shown in FIG. 8, setscrew 46 includes a first gauge 70 a, a second gauge 70 b and a third gauge 70 c, wherein gauges 70 a, 70 b, 70 c form a radial pattern, with gauges 70 a, 70 b, 70 c each positioned 120 degrees from an adjacent one of gauges 70 a, 70 b, 70 c. One angle indication in FIG. 8 shows the 120 degree relationship between adjacent gauges 70 and another angle indication in FIG. 8 shows an angle between one of gauges 70 and a vertical axis. In some embodiments, gauges 70 a, 70 b, 70 c, 70 d each include the same type of strain gauge. In some embodiments, at least one of gauges 70 a, 70 b, 70 c, 70 d is different than at least one other of gauges 70 a, 70 b, 70 c, 70 d. For example, in one embodiment, gauges 70 a, 70 d are radial strain gauges and gauges 70 b, 70 c are circumferential strain gauges. In some embodiments, two of gauges 70 a, 70 b, 70 c, 70 d are positioned in a radial direction and two of gauges 70 a, 70 b, 70 c, 70 d are positioned in a tangential direction. That is, two of gauges 70 a, 70 b, 70 c, 70 d are oriented about a radius of setscrew 46 and two of gauges 70 a, 70 b, 70 c, 70 d are positioned along a tangential line of setscrew 46.

Further regarding position of gauge(s) 70, there are benefits to controlling orientation of gauges 70. Doing so can result in more-accurate loading data. For example, in some embodiments, the orientation of gauges 70 must have a direct relationship to rod 38 when rod 38 is positioned in cavity 36. In one embodiment, the orientation of gauges 70 must be inline with rod 38 when rod 38 is positioned in cavity 36, as shown in FIG. 2. In one embodiment, the orientation of gauges 70 must be transverse to rod 38 when rod 38 is positioned in cavity 36. In one embodiment, the orientation of gauges 70 must be at an acute angle relative to rod 38 when rod 38 is positioned in cavity 36.

In order to position gauges 70 at a selected orientation relative to rod 38, thread form 54 is timed and/or clocked with thread form 44 such that gauges 70 will be positioned at the selected orientation relative to rod 38 when thread form 54 is fully threaded with thread form 44. In some embodiments, the timing and/or clocking of thread form 54 with thread form 44 is determined by the positioning of a start 76 of thread form 54 located at distal end 77. As shown in FIG. 4, distal end 77 includes height H that is a controlled dimension used to define the position and/or orientation of start 76. Start 76 is selectively positioned along thread form 54 such that gauges 70 will be positioned at the selected orientation relative to rod 38 when thread form 54 is fully threaded with thread form 44. In some embodiments, setscrew 46 is prevented from being rotated relative to head 24 in a rotational direction, such as, for example, clockwise, when thread form 54 is fully threaded with thread form 44. In some embodiments, start 76 is selectively positioned along thread form 54 such that gauges 70 will be positioned at the selected orientation relative to rod 38 when thread form 54 is fully tightened with thread form 44. In some embodiments, start 76 is selectively positioned along thread form 54 such that gauges 70 will be positioned at the selected orientation relative to rod 38 when setscrew 46 is prevented from translating axially in one direction relative to head 24 by rod 38. That is, gauges 70 will be positioned at the selected orientation relative to rod 38 when tip 56 first engages rod 38 such that rod 38 is fixed relative to head 24.

In some embodiments, system 20 includes one or more components that allow gauges 70 to send and/or analyze the measurements from gauges 70 relating to force between setscrew 46 and rod 38. For example, in one embodiment, shown in FIGS. 9-12, a load-sensing assembly 78 includes an antenna 80, such as a radio frequency identification (RFID) coil, a near field-communication (NFC) antenna or other short-range communication transmitter and/or receiver. In some embodiments, assembly 78 includes one or more integrated circuits 82 such as, for example, an RFID chip or an NFC chip. In some embodiments, assembly 78 includes one or more electronics components 84 and gauges 70. In some embodiments, assembly 78 is the same or similar to the load sensing assembly disclosed in U.S. Ser. No. 16/039,592, which is expressly incorporated herein by reference, in its entirety.

In some embodiments, electronics components 84 include a flexible electronics component, such as, for example, a flex circuit or one or more electrical circuits. In some embodiments, antenna 80 may be operably connected to electronics component 84 via a connecting member 86. For example, as shown in FIG. 9, member 86 may be connected to both antenna 80 and electronics component 84. In some embodiments, member 86 is positioned perpendicularly to both antenna 80 and electronics component 84. In some embodiments, member 86 and antenna 80 may be constructed integrally or may be separately constructed and attached together in any suitable manner, such as for example by adhesive, chemical, mechanical or cement bonding. In some embodiments, member 86 and electronics component 84 may be constructed integrally or may be separately constructed and attached together in any suitable manner, such as for example by adhesive, chemical, mechanical or cement bonding.

In some embodiments, circuit 82 is operably connected to electronics component 84. As shown in FIG. 9, electronics component 84 may have a top surface 88 and a bottom surface 90. Circuit 82 may be positioned on surface 88 of electronics component 84, and may be connected to surface 88 in any suitable manner, including, for example, adhesive, chemical, mechanical or cement bonding. Circuit 82 may include a memory 82 a according to an embodiment. Memory 82 a may be used to store various information. For example, one or more measurements of one or more of gauges 70 may be stored in memory 82 a. In some embodiments, a unique identifier associated with assembly 78, a component thereof, or setscrew 46 may be stored in memory 82 a. Additional and/or alternate information or types of information may be stored according to this disclosure.

In some embodiments, one or more of gauges 70 may be operably connected, for example by adhesive, cement, mechanical or chemical bonding, to electronics component 84. For example, one or more of gauges 70 may be operably connected to electronics component 84 via surface 90 of electronics component 84. One or more of gauges 70 may be connected to surface 90 of electronics component 84 in any suitable manner including, without limitation, via an adhesive bonding agent.

As shown in FIG. 9, antenna 80 may have a generally curved shape. Antenna 80 may include a first end and a second end. Antenna 80 may include an opening that extends from the first end toward the second end, as shown in FIG. 9. As shown in FIG. 10, assembly 78 may be configured to be mounted to setscrew 46. Antenna 80 is sized to extend around setscrew 46 such that circuit 82, electronics component 84, gauges 70 and member 86 are positioned within socket 62, recess 64 and/or groove 74. Antenna 80 may circumferentially surround at least a portion of the exterior of setscrew 46. In one embodiment, shown in FIG. 11, antenna 80 may be positioned at least partially inside of socket 62. In some embodiments, gauges 70 may be connected to setscrew 46 in any suitable manner including, without limitation via an adhesive. FIG. 12 illustrates a top view of assembly 78 mounted to setscrew 46.

In various contemplated embodiments, any activity described herein can be performed by a specially configured computer, or system or network of computers. Activities can performed by the computing device or system based on any of various input, including from one or more implanted gauges and one or more of the readers or smart tools or instruments described herein. The computing device or system can process, in performing the activities, big data or other information, such as profile or historic diagnostics data, about a subject patient and/or any number of other patients or persons. Example computing activities include but are not limited to: (i) collecting, organizing, or otherwise processing data received; (ii) monitoring gauge or patient status, (iii) transmitting alerts, notifications, or data, received or processed, to any desired destination (to, e.g., patient or hospital device) for consideration or further use; (iv) determining patterns in gauge or patient changes of state, or adherence to patterns; and (v) diagnostics.

In various contemplated embodiments, the specially configured computer, or system or network of computers is/are configured to provide diagnostic feedback. In some embodiments, the specially configured computer, system or network of computers communicate(s) with coils located outside a patient for powering electronic components of system 20, such as, for example, gauges 70. In some embodiments, the specially configured computer, system or network of computers communicate(s) with electronic components that provide remote power options using telemetry, such as, for example, NFC. In some embodiments, the electronic components include a NFC power harvesting integrated circuit. In some embodiments, the electronic components include an analog front end integrated circuit. In some embodiments, the electronic components include a microprocessor integrated circuit. In some embodiments, the electronic components are configured to provide diagnostic feedback to guide and/or determine an optimum location for an external coil for powering components of system 20, such as, for example, gauges 70. In some embodiments, the electronic components include resonant circuits that provide an auto tuning feature to optimize communication between components of system 20, such as, for example, gauges 70, and the remote power source. In some cases, various factors may contribute to detuning a resonant circuit, for example, implant depth, metal in the vicinity both inside and outside a body, and/or other factors. In some embodiments, the electronic components have an auto tuning feature and/or method that includes changing a tuning capacitor value and/or shifting operating frequency+/− over a range relative to a selected frequency. In some embodiments, the external coil and associated circuitry includes an auto tuning feature to optimize communication between the electronic components and the remote power source, and/or other components of system 20.

In some embodiments, the NFC device remotely communicates with a device, such as, for example, a computer that is disposed outside or external to the patient's body to transfer, transmit and/or receive data relating to gauges 70. Gauges 70 may include diagnostic sensor electronics connected with one or more sensors. The diagnostic sensor electronics may comprise various commercially available integrated circuit devices, see, for example, but not limited to, the AD5933 Impedance Converter Network Analyzer distributed by Analog Devices. The integrated circuit device may comprise various commercially available integrated circuit devices, see, for example, but not limited to, the RF430 microcontroller distributed by Texas Instruments RF430.

In some embodiments, the diagnostic sensor electronics and/or the analog device gather information from gauges 70, such as, for example, loading information, pressure information, tension information, motion information, alignment or misalignment information and/or temperature, relating to one or more components of system 20, as described herein. The computer remotely communicates with the NFC device, as described herein, to collect data from gauges 70 via the diagnostic sensor electronics. In some embodiments, a reader communicates with the computer. The reader emits a small electric current that creates a magnetic field to bridge the physical space between the reader and gauges 70. The electric field is received by the NFC device and converted into electrical impulses to communicate data and diagnostics, relating to gauges 70 to the computer, as described herein.

The diagnostic sensor electronics provides feedback and/or measure one or more diagnostic conditions. The diagnostic sensor electronics sense and transmit to the computer various diagnostic indicia, and in some embodiments, diagnose and respond to such measurements, such as, for example, in the context of a spinal implant surgery. In some embodiments, a surgeon can monitor a patient after surgery, and make adjustments to one or more components of system 20. In some embodiments, this configuration allows one or more components of system 20 to be corrected or modified based on changes that take place subsequent to surgery, and/or for selected and remote changes to diagnostic conditions inside the patient's body. In some embodiments, the diagnostic sensor electronics indicate a fusion rate of vertebrae. In some embodiments, one or more measurements obtained by one or more of gauges 70 may be stored by circuit 82 of assembly 78, such as, for example, in memory 82 a of circuit 82. Circuit 82 may be interrogated by a reader 83. For example, an RFID chip may be read by an RFID reader. As another example, an NFC chip of circuit 82 may be read by or may otherwise communicate with an NFC reader or other NFC-enabled device. A reader may interrogate circuit 82 when in a certain proximity to circuit 82. In some embodiments, a reader may interrogate circuit 82 after circuit 82 has been implanted into a patient within setscrew 46. In some embodiments, circuit 82 may communicate with a reader or other electronic device without being interrogated.

Circuit 82 may transmit one or more measurements to the reader. This transmission may occur in response to being interrogated by the reader, or the transmission may be initiated by circuit 82. The reader may receive the transmitted measurements, and may cause at least a portion of the measurements to be displayed to a user. For example, a physician may use a reader to interrogate an RFID chip of a patient's implant, such as, for example bone screw 22, rod 38 or setscrew 46. The reader may include a display, or may be in communication with a display device, which may display at least a portion of the measurements received from the RFID chip.

In some embodiments, circuit 82 is passive such that the chip has no internal power source and is powered by the energy transmitted from a reader. In such embodiments, circuit 82 may not transmit information until interrogated by a reader. In some embodiments, circuit 82 may be active such that the chip is battery-powered and capable of broadcasting its own signal. Active circuit 82 may transmit information in response to be interrogated by a reader, but also on its own without being interrogated. For example, active circuit 82 may broadcast a signal that contains certain information such as, for example, one or more measurements gathered by one or more of gauges 70. Active circuit 82 may continuously broadcast a signal, or it may periodically broadcast a signal. Power may come from any number of sources, including, for example, thin film batteries with or without encapsulation or piezo electronics.

In some embodiments, one or more sensors of gauges 70 may transmit information by directly modulating a reflected signal, such as an RF signal. The sensors of gauges 70 may form a Wireless Passive Sensor Network (WPSN), which may utilize modulated backscattering (MB) as a communication technique. External power sources, such as, for example, an RF reader or other reader, may supply a WPSN with energy. The sensor(s) of the WPSN may transmit data by modulating the incident signal from a power source by switching its antenna impedance.

One or more measurements received from assembly 78 may be used to make determinations of the condition of a spinal implant and/or treatment of a spinal disorder. For instance, proper placement of rod 38 and/or setscrew 46 may result in an acceptable range of force measurements collected by gauges 70. Measurements outside of this range may indicate a problem with the placement or positioning of rod 38 and/or setscrew 46, such as, for example, loosening of setscrew 46, failure or rod 38, yield or fracture/breakage, improper torque, breakage of the bone segment or portion, the occurrence of fusion or amount of fusion, and/or the like.

One or more tools or instruments may include a reader which may be used to gather information from circuit 82 during or in connection with a procedure. For instance, a torque tool may be used to loosen or tighten setscrew 46. A torque tool may include a reader, or may be in communication with a reader, such that a user of the torque tool is able to obtain, in substantially real time, one or more measurements relating to setscrew 46 and rod 38 placement that are measured by gauges 70 via the tool. For example, as a user is applying torque to setscrew 46, the user may see one or more force measurements between setscrew 46 and rod 38 in order to determine that the positioning of setscrew 46 and/or rod 38 is correct and that the proper force is being maintained. In some embodiments, a tool or instrument may include a display device on which one or more measurements may be displayed. In some embodiments, a tool or instrument may be in communication with a display device, and may transmit one or more measurements for display on the display device via a communications network.

In some embodiments, an electronic device, such as a reader or an electronic device in communication with a reader, may compare one or more measurements obtained from circuit 82 to one or more acceptable value ranges. If one or more of the measurements are outside of an applicable value range, the electronic device may cause a notification to be made. For example, an electronic device may generate an alert for a user, and cause the alert to be displayed to the user via a display device. Alternatively, an electronic device may send an alert to a user such as via an email message, a text message or otherwise.

In some embodiments, circuit 82 may store a unique identifier associated with setscrew 46. Circuit 82 may transmit the unique identifier to an electronic device. For example, when a reader interrogates circuit 82, circuit 82 may transmit a unique identifier for setscrew 46 that is stored by circuit 82 to the reader. Having access to a unique identifier for setscrew 46 may help a user ascertain whether the measurements that are being obtained are associated with setscrew 46. Also, having access to a unique identifier for setscrew 46 may help a user take inventory of one or more components. For instance, after spinal surgery, a physician or other health care professional may use a reader to confirm that all of the setscrews allocated for the procedure have been used and are positioned in a patient.

In assembly, operation and use, surgical system 20, similar to the systems and methods described herein, is employed with a surgical procedure for treatment of a spinal disorder affecting a section of a spine of a patient, as discussed herein. The components of surgical system 20 are employed with a surgical procedure for treatment of a condition or injury of an affected section of the spine, such as, for example, vertebrae.

In use, to treat a selected section of vertebrae, a medical practitioner obtains access to a surgical site in any appropriate manner, such as through incision and retraction of tissues. In some embodiments, surgical system 20 can be used in any existing surgical method or technique including open surgery, mini-open surgery, minimally invasive surgery and percutaneous surgical implantation, whereby vertebrae are accessed through a mini-incision, or sleeve that provides a protected passageway to the area. Once access to the surgical site is obtained, the particular surgical procedure can be performed for treating the spine disorder.

An incision is made in the body of a patient and a cutting instrument creates a surgical pathway for implantation of components of surgical system 20. A preparation instrument can be employed to prepare tissue surfaces of vertebrae as well as for aspiration and irrigation of a surgical region. A pilot hole is made in a vertebra for receiving shaft 26. Shaft 26 is positioned in the pilot hole and is rotated relative to the vertebra using a driver, for example, such that thread form 48 directly engages tissue to drive shaft 26 into to the vertebra. Shaft 26 may be driven into the vertebrae a selected amount to fix shaft 26 relative to the vertebra. Once shaft 26 is sufficiently fixed relative to the vertebra, head 24 is connected with shaft 26. In some embodiments, head 24 is configured to snap onto shaft 26 to prevent head 24 from unintentionally being removed from shaft 26. A spinal construct, such as, for example, rod 38 is inserted into cavity 36. Once rod 38 is positioned in cavity 36, thread form 54 is aligned with thread form 44 and setscrew 46 is rotated relative to head 24 in a rotational direction, such as, for example, clockwise such that thread form 54 engages thread form 44. Further rotation of setscrew 46 relative to head 24 causes setscrew 46 to translate relative to head 24 such that tip 56 moves toward rod 38. Setscrew 46 is rotated relative to head 24 until tip 56 directly engages rod 38 and/or thread form 54 is fully threaded with thread form 44. Because thread form 54 is timed and/or clocked with thread form 44 to position gauges 70 at a selected orientation relative to rod 38 when rod 38 is positioned in cavity 36, gauges 70 will be positioned at the selected orientation relative to rod 38 when tip 56 directly engages rod 38 and/or thread form 54 is fully threaded with thread form 44.

One or more measurements obtained by gauges 70 are stored by circuit 82 of assembly 78, such as, for example, in memory 82 a of circuit 82. In some embodiments, circuit 82 is interrogated by a reader to transmit the measurements obtained by gauges 70 to the reader. For example, an RFID chip of circuit 82 may be read by an external RFID reader. Alternatively, an NFC chip of circuit 82 may be read or otherwise communicate with an external NFC reader or other NFC-enabled device. In some embodiments, the reader interrogates circuit 82 when the reader is within a certain distance of circuit 82 to transmit the measurements obtained by gauges 70 to the reader. In some embodiments, circuit 82 may to transmit the measurements obtained by gauges 70 to the reader without the reader being interrogated. The reader can cause one or more of the measurements obtained by gauges 70 to be displayed on the reader itself or a separate display, such as, for example, a computer monitor.

The measurements obtained by gauges 70 are displayed to provide an in vivo assessment of the bony incorporation of an autograft, for example, and thus the fusion of the autograft and vertebrae. In some embodiments, the measurements obtained by gauges 70 are compared with an expected pattern of strain. If the data from gauges 70 follows or deviates from the expected patterns, conclusions can be drawn about progress of the fusion between the autograft and the vertebrae. In some embodiments, a surgeon may perform one or more procedures to improve the fusion between the autograft and the vertebrae, based on the in vivo assessment. In that gauges 70 may be configured to continuously provide measurements that can be read and displayed, system 20 thus provides the ability to continuously, or on-demand, monitor fusion progress and biomechanical performance during the post-operative period by assessing strain data from gauges 70. Indeed, strain readings from gauges 70 may be used to develop an accurate, early assessment of the fracture healing rate and the potential for not uniting. An early diagnosis of delayed union is advantageous because it allows the surgeon to take remedial steps as soon as a possible non-union is suspected, thus prompting intervention. Because of this ability to continuously or on-demand monitor fusion progress and biomechanical performance, it may be possible to appropriately time, or even avoid, additional surgery.

Upon completion of a procedure, as described herein, the surgical instruments, assemblies and non-implanted components of surgical system 20 are removed and the incision(s) are closed. One or more of the components of surgical system 20 can be made of radiolucent materials such as polymers. Radiomarkers may be included for identification under x-ray, fluoroscopy, CT or other imaging techniques. In some embodiments, surgical system 20 may include one or a plurality of spinal rods, plates, connectors and/or bone fasteners for use with a single vertebral level or a plurality of vertebral levels.

In some embodiments, one or more bone screws, as described herein, may be engaged with tissue in various orientations, such as, for example, series, parallel, offset, staggered and/or alternate vertebral levels. In some embodiments, one or more of the bone screws may comprise multi-axial screws, sagittal adjusting screws, pedicle screws, mono-axial screws, uniplanar screws, facet screws, fixed screws, tissue penetrating screws, conventional screws, expanding screws, wedges, anchors, buttons, clips, snaps, friction fittings, compressive fittings, expanding rivets, staples, nails, adhesives, posts, fixation plates and/or posts.

In one embodiment, surgical system 20 includes an agent, which may be disposed, packed, coated or layered within, on or about the components and/or surfaces of surgical system 20. In some embodiments, the agent may include bone growth promoting material, such as, for example, bone graft to enhance fixation of the components and/or surfaces of surgical system 20 with vertebrae. In some embodiments, the agent may include one or a plurality of therapeutic agents and/or pharmacological agents for release, including sustained release, to treat, for example, pain, inflammation and degeneration.

FIG. 13 illustrates a top down view showing a set screw 46 for use with a surgical system 20. In various embodiments, set screw 46 may include an similar arrangement of foil strain gauges 100 as disclosed above. As used herein, the term “foil strain gauge” may have its ordinary technical meaning as would be understood by a person of ordinary skill in the art. For example, a foil strain gauge 100 may refer to a sensor for measuring relative changes in the length of a material (strain) due to applied forces that cause deformation. In various instances, a deformation may include either compression or tension and may measure various strains and/or applied forces. In various embodiments, it shall be appreciated that various configurations and types of strain gauges may be utilized and embodiments in accordance with the principles of this disclosure may utilize any number and type of strain gauges including configurations where all strain gauges in any one embodiment may not be of the same type. A non-exhaustive and non-limiting example listing of strain gauges may include linear strain gauges, rosette foil strain gauges, torsion/shear strain gauges, double linear foil strain gauges, full bridge strain gauges, chain foil strain gauges, and interconnected foil strain gauges. A linear strain gauge may measure strain across a single plane of direction, for example. A rosette foil strain gauge may utilize dual measuring grids to offset strain measurements at approximately a 90° angle to measure biaxial stress, for example. A torsion strain gauge and/or shear strain gauge may feature various measuring grids that are arranged for determining the shear stress, for example. A double linear foil strain gauges may include parallel measuring grids for acquiring perpendicular stress, for example. A full bridge strain gauge may feature a plurality of integrated measuring grids for robust strain measurements of shear stresses in tension and compression for example. For example still, a plurality of integrated measuring grids may be selectively disposed at distinct locations of a set screw, for example. A chain foil strain gauge may be equipped with a number of smaller measuring grids to acquire shear force gradients, for example. It shall be appreciated that any type of strain gauge may be employed by various embodiments disclosed herein in any number, arrangement, and combination in accordance with the principles of this disclosure.

In the example embodiment of FIG. 13, it is shown that four arcuate and/or curved strain gauges 100 a, 100 b, 100 c, 100 d are symmetrically disposed around a lower interior surface 72 of the set screw 46. In some embodiments, gauges 100 directly engage a surface 72 of setscrew 46 that defines a groove 74 that is distal to recess 64, for example as shown in FIG. 5. In the example embodiment, a first strain gauge 100 a may have a substantially consistent width and a curved profile that approximates the curved profile of the set screw 46. For example, an outer edge of first strain gauge 100 a may extend along a curved path having a perimeter and/or length that remains at substantially the same distance away from an outermost edge of surface 72. That is to say that the curvature of strain gauge 100 corresponds to the curvature of surface 72, at least in plan view, for example. In various embodiments, the second strain gauge 100 b, third strain gauge 100 c, and fourth strain gauge 100 d, may have the same, similar, and or substantially the same properties as first strain gauge 100 a. For example, the strain gauges 100 a, 100 b, 100 c, and 100 d may have the same, similar, and our substantially the same geometrical relationship to the outermost edge of surface 72. Additionally, each of the first through fourth strain gauges 100 a, 100 b, 100 c, 100 d, may be the same, substantially the same, and or similar to one another in that they may have the same shape and size, for example.

In various embodiments, in a plan view looking down at surface 72, the location of each of the first, second, third, and fourth strain gauges 100 a, 100 b, 100 c, 100 d may be understood as being positioned in one of four quadrants, respectively. For example, in dividing surface 72 into four equally sized quadrants and disposing each of the first, second, third, and fourth strain gauges 100 a, 100 b, 100 c, 100 d in a respective quadrant and at substantially the same distance from the outermost edge of surface 72, for example. Additionally, in at least some embodiments a centrally disposed fifth strain gauge 100 e may be provided. Fifth strain gauge 100 e may be shaped like a circle and may be disposed at a relative center of surface 72 and or set screw 46. In various embodiments, fifth strain gauge 100 e may be positioned directly above tip 56, for example see FIG. 5. Additionally, in the example embodiment each of the first, second, third, and fourth strain gauges 100 a, 100 b, 100 c, 100 d may be symmetrically disposed around fifth strain gauge 100 e where the innermost edge of the first, second, third, and fourth strain gauges 100 a, 100 b, 100 c, 100 d extend in a curved path that remains at substantially the same distance away from an outermost edge of the circular shaped fifth strain gauge 100 e.

In various embodiments, distinct advantages are realized by the above disclosed arrangement of sensors 100 a, 100 b, 100 c, 100 d, and 100 e. For example, a multi quadrant multi track system may provide more meaningful and reliable sensor data and/or remote assessment of fusion status and hardware integrity. In some embodiments, the various electrical signals and their corresponding stress/strain generated by 100 a, 100 b, 100 c, 100 d, and 100 e may be averaged to acquire a more accurate assessment of the actual conditions of which set screw 46 is experiencing. In other systems utilizing a single strain gauge and or other strain gauges that are not symmetrically distributed (not illustrated) such average assessments may not be possible and/or may not be accurate. Embodiments in accordance with the principles of a symmetrically disposed system as explained above, are not as susceptible to the final torque applied and the final position of the set screw relative to the tulip head 24 and pedicle screw. Additionally, while care is taken to produce a uniform system 20 of tolerances in accordance with prevailing standards those with skill in the art will appreciate that variations can occur. For example, due to manufacturing processes, the installation process itself, damage during transit, etc. can all lead to minute differences and/or damage to a set screw. In providing a multi quadrant approach including a plurality of foil based strain gauges 100 a, 100 b, 100 c, 100 d, and optionally 100 e these variations may be accounted for due to averaging of the various readings and measurements. Stated another way, various multi-track and multi-quadrant foil strain gauge approaches disclosed herein provide more reliable and meaningful data that is significantly less susceptible to the variations in set screws themselves and variations that may occur due to the torque down process and or set screw installation process. Accordingly, reliable data and patient care may be achieved.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplification of the various embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. 

What is claimed is:
 1. A medical construct comprising: a set screw extending along a longitudinal axis between a proximal portion and a distal portion, set screw comprising: an outside thread form; a socket disposed within an interior of the set screw relative to the outside thread form, the socket extending parallel to the longitudinal axis and having a lower surface; and a plurality of strain gauges disposed on the lower surface, the plurality of gauges being configured to measure a force applied to the set screw, wherein each of the plurality of strain gauges are symmetrically disposed with respect to the lower surface.
 2. The medical construct recited in claim 1, wherein the lower surface comprises an edge portion defined by a radius of a circle.
 3. The medical construct recited in claim 2, wherein each of the plurality of strain gauges comprises an outer curved edge approximating a curvature of the edge portion of the lower surface.
 4. The medical construct recited in claim 3, wherein the plurality of strain gauges includes a first strain gauge, a second strain gauge, a third strain gauge, and a fourth strain gauge.
 5. The medical construct recited in claim 4, wherein: the first strain gauge is disposed in a first quadrant of the lower surface; the second strain gauge is disposed in a second quadrant of the lower surface; the third strain gauge is disposed in a third quadrant of the lower surface; and the fourth strain gauge is disposed in a fourth quadrant of the lower surface.
 6. The medical construct recited in claim 1, wherein the lower surface extends in a direction that is substantially perpendicular to the longitudinal axis.
 7. The medical construct recited in claim 6, wherein the lower surface comprises a curved edge portion defined by a radius of a circle.
 8. The medical construct recited in claim 7, wherein the plurality of strain gauges includes a first strain gauge, a second strain gauge, a third strain gauge, and a fourth strain gauge.
 9. The medical construct recited in claim 8, wherein: the first strain gauge comprises a first outer curved edge approximating a curvature of the curved edge portion of the lower surface; the second strain gauge comprises a second outer curved edge approximating the curvature of the curved edge portion of the lower surface; the third strain gauge comprises a third outer curved edge approximating the curvature of the curved edge portion of the lower surface; and the fourth strain gauge comprises a fourth outer curved edge approximating a curvature of the curved edge portion of the lower surface.
 10. The medical construct recited in claim 9, wherein a first distance between the first outer curved edge of the first strain gauge and the curved edge portion of the lower surface remains substantially the same along a length of the first outer curved edge; a second distance between the second outer curved edge of the second strain gauge and the curved edge portion of the lower surface remains substantially the same along a length of the second outer curved edge; a third distance between the third outer curved edge of the third strain gauge and the curved edge portion of the lower surface remains substantially the same along a length of the third outer curved edge; and a fourth distance between the fourth outer curved edge of the second strain gauge and the curved edge portion of the lower surface remains substantially the same along a length of the fourth outer curved edge.
 11. The medical construct recited in claim 10, wherein the first distance, the second distance, the third distance, and the fourth distance are substantially the same.
 12. The medical construct recited in claim 1, wherein the plurality of strain gauges are interconnected.
 13. The medical construct recited in claim 1, wherein at least one of the plurality of strain gauges is chosen from the group consisting of: a linear strain gauge, a rosette foil strain gauge, a torsion strain gauges, a double linear foil strain gauge, a full bridge strain gauges, and a chain foil strain gauges.
 14. A medical construct comprising: a set screw extending along a longitudinal axis between a proximal portion and a distal portion, set screw comprising: an outside thread form; an interior socket, the socket extending parallel to the longitudinal axis and having a circular lower surface; and a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, and a fifth strain gauge; wherein: each of the first, second, third, and fourth strain gauges are symmetrically disposed with respect to the lower surface, and the fifth strain gauge is disposed within a center portion of the lower surface.
 15. The medical construct recited in claim 14, wherein each of the first, second, third, and fourth strain gauges are symmetrically disposed within a respective quadrant of the lower surface.
 16. The medical construct recited in claim 15, wherein the set screw further comprises a hemispherical tip portion at the distal end that is coaxially aligned with the longitudinal axis.
 17. The medical construct recited in claim 16, wherein the fifth strain gauge is substantially shaped like a circle and a center point of the fifth strain gauge is coaxially aligned with the longitudinal axis.
 18. The medical construct recited in claim 14, wherein: the circular surface comprises an outer edge portion having a substantially consistent curvature, the first strain gauge comprises a first outer curved edge approximating the curvature of the curved edge portion of the lower surface; the second strain gauge comprises a second outer curved edge approximating the curvature of the curved edge portion of the lower surface; the third strain gauge comprises a third outer curved edge approximating the curvature of the curved edge portion of the lower surface; and the fourth strain gauge comprises a fourth outer curved edge approximating a curvature of the curved edge portion of the lower surface.
 19. The medical construct recited in claim 18, wherein the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge have substantially the same size and shape.
 20. The medical construct recited in claim 19, wherein: the outside thread form of the set screw is configured to be inserted within and mate with an internal thread form of a tulip head connector, the tulip head connector comprising a receiving cavity configured to receive a longitudinal rod, a lower portion of the tulip head connector is configured to couple to a pedicle screw, the set screw is configured to secure the longitudinal rod within the receiving cavity, the first strain gauge, second strain gauge, third strain gauge, fourth strain gauge, and fifth strain gauge are configured to provide an independent strain applied to the set screw, respectively, and each independent strain is indicative of an average load between the longitudinal rod and the set screw. 